1. Field of the invention
The present invention relates to a recording/reproducing apparatus for recording and reproducing signals of video, audio or other information data on and from a tape-like recording medium such as a magnetic recording tape, and particularly to a recording/reproducing apparatus capable of editing the recorded data. The editing is a function of varying the recorded data including data replacement or erase in a given recording area and additional data recording in an area continuously succeeding a given recording area.
2. Description of the Prior Art
A variety of magnetic recording/reproducing apparatuses such as the video tape recorders (referred to as VTRs hereinafter) utilizing magnetic recording tapes have been developed and practically used. They have recently been reduced in size, improved for high density recording, and implemented for digital recording. It is essential for increasing the recording density and maintaining the compatibility to perform accurate tracking action of the magnetic head. To realize the accurate tracking action, a tracking control method called ATF (Automatic Track Finding) has been introduced for use in a VTR in which a pilot signal is mixed into a data signal during recording and utilized for correct tracking action during retrieval of the data signal. A conventional magnetic recording/reproducing apparatus using such a tracking control method will now be described.
In a recording mode, a row of oblique recording tracks are formed on a magnetic recording tape by a magnetic head mounted on a rotary cylinder. A recording signal fed to the magnetic head contains a data signal mixed with pilot signals for tracking control. More specifically, two different pilot signals having frequencies of f1 and f2 respectively are recorded alternately onto every two recording tracks. Usually, the frequency of each pilot signal is selected from one to four low frequencies which will hardly interfere with the data signal.
The action of tracking the recording tracks in a reproducing mode will be explained. The magnetic head tracing a target track reads a segment of the data signal and simultaneously detects two pilot signal components f1 and f2 from the adjacent recording tracks at both sides of the target track. The relative position of the magnetic head to the target track can hence be examined through comparing the amplitudes of the two pilot components f1, f2. In more detail, the two pilot components f1, f2 are extracted through a bandpass filter and converted by an amplitude detection circuit to their respective DC components depending on their amplitudes. The two DC components are then compared by a subtraction circuit. A resultant output of the subtraction circuit is a tracking error signal exhibiting a positional difference between the magnetic head and the target track to be traced. Upon receiving the tracking error signal, a capstan motor control circuit for controlling the feeding of the tape adjusts a capstan motor to control the tape running so that the magnetic head traces along the center of the target track.
For replacement of the recorded data signal on a magnetic recording tape with another data signal (which will hereafter be referred to as insert editing), the reproducing mode is shifted to the recording mode at a start point of rewriting and the new data signal is recorded while the existing data signal is being erased. More specifically, the new data signal is recorded onto the recording tape track by track at the timing determined by a signal from a rotating position detecting sensor which is generally called PG (Pulse Generator) mounted on the rotary cylinder.
According to the conventional magnetic recording/reproducing apparatus, since the tracking is conducted using the pilot signals mixed into the data signal, no pilot signals will be given during the insert editing action. This will result in failure in the time matching between a current track and a preceding track at the end of editing, sequence error of the pilot signals carried on the data signal, and remaining of track which has imperfect track width. In case that the apparatus has several recording modes such, for example, as a standard play (referred to as SP hereinafter) mode and a long play (referred to as LP hereinafter) mode, the conventional apparatus gives no signal for indicating the recording mode of recording tracks during the editing. Thus it may happen that the apparatus edits the tracks in a different recording mode. Further, since the conventional apparatus determines the start point of recording on each track for insert editing action by the signal from the PG, the existing data signal on the track will hardly be erased in entirety due to mechanical non-uniformity of the rotary cylinder and setting error of the PG. The remaining, non-erased data may result in malfunction of the entire apparatus. Also, excessive erasing in the same track will likely be caused during partial rewriting. Particularly, editing with another recording/reproducing apparatus may create much errors, thus degrading the performance of the apparatus.